About Mosquito Bites

Key points

  • Female mosquitoes bite people and animals to get a blood meal.
  • Most female mosquitoes cannot produce eggs without a blood meal.
  • Male mosquitoes do not bite people and animals.
  • People react differently to mosquito bites.
Photo showing multiple mosquito bites on a person's forearm and a U.S. quarter to show scale

What happens when a mosquito bites you

When a mosquito bites you, it pierces the skin using a special mouthpart (proboscis) to suck up blood. As the mosquito is feeding, it injects saliva into your skin. Your body reacts to the saliva resulting in a bump and itching.

Some people have only a mild reaction to a bite or bites. Other people react more strongly, and a large area of swelling, soreness, and redness can occur.

A mosquito biting a person's arm
The body reacts to mosquito saliva following a blood meal.

Signs and symptoms

Mosquito bite signs

  • A puffy and reddish bump appearing a few minutes after the bite
  • A hard, itchy, reddish-brown bump, or multiple bumps appearing a day or so after the bite or bites
  • Small blisters instead of hard bumps
  • Dark spots that look like bruises

Severe reactions can occur

  • In children
  • In adults bitten by mosquito species they haven't been exposed to previously
  • In people with immune system disorders

More severe reactions

  • A large area of swelling and redness
  • Low-grade fever
  • Hives
  • Swollen lymph nodes
Photo showing multiple mosquito bites on a person's forearm
Mosquito bites can become swollen, red, and itchy.


Infected bite

  • Do not scratch bites. They can become infected.
  • An infected bite may appear red, feel warm, or a red streak may spread outward from the bite.
  • See a healthcare provider if symptoms worsen.

Mosquito-borne germs

  • Mosquitoes spread germs (viruses, parasites) through bites that can make you sick.
    • Viruses like West Nile, dengue, Zika
    • Parasites like malaria
  • A mosquito gets infected with a germ when it bites a person or animal that is infected.
  • The infected mosquito can spread germs to other people or animals through bites.
  • Not everyone infected with a mosquito-borne germ gets sick.

Mosquito-borne viruses

Mosquito-borne parasites



  • Wash the bite and surrounding area with soap and water.
  • Apply an ice pack for 10 minutes to reduce swelling and itching. Reapply ice pack as needed.
  • Apply a mixture of baking soda and water, which can help reduce the itch response.
    • Mix 1 tablespoon baking soda with just enough water to create a paste.
    • Apply the paste to the mosquito bite.
    • Wait 10 minutes.
    • Wash off the paste.
  • Use an over-the-counter anti-itch or antihistamine cream to help relieve itching. Follow the product label directions.